Method and apparatus for producing a semi-continuous filament yarn



Dec. 24, 1968 mm W *VMVIIQ hwy l|w G. A. WATSON SEMI-CONTINUOUS FILAMENTYARN Filed July 3, 1967 METHOD AND APPARATUS FOR PRODUCING A N OmINVENTOR GEORGE A.WATSON ATTORNEY United States Patent 3,417,560 METHODAND APPARATUS FOR PRODUCING A SEMI-CONTINUOUS FILAMENT YARN George A.Watson, Charlotte, N.C., assignor to Celanese Corporation, New York,N.Y., a corporation of Delaware Continuation-impart of application Ser.No. 382,263, July 13, 1964. This application July 3, 1967, Ser. No.650,795

15 Claims. (Cl. 5734) ABSTRACT OF THE DISCLOSURE A method, apparatus andproduct comprising producing a semi-continuous filament yarn havingstaple yarn characteristics from crimped tow comprising longitudinallyslitting a deregistered tow into strips of filaments either with orwithout a tow spreading stage and subsequently twisting the strips intoyarn.

Background of the invention This is a continuation-in-part of SN.382,263, filed July 13, 1964, now abandoned.

This invention relates to the production of continuous filament yarnfrom continuous filament fibers and more particularly to the productionof yarn from a tow of deregistered crimped filaments.

The deregistration or opening of a tow of continuous crimped filamentsis known in the art. Previously, such deregistration was effected in theproduction of cigarette tow in a manner described by Dunlap et al. inUS, 3,156,016.

It is an object of the present invention to provide a method for theproduction of a novel, substantially continuous filament yarn. It isanother object of this invention to provide a bulky yarn ofsubstantially continuous filaments wherein the fiber length averagesabout 6 inches or more. A further object of this invention is to providean apparatus for the production of said yarn. These and other objectswill become apparent to those skilled in the art from a description ofthe invention which follows.

Summary of the invention In accordance with the invention, a method forproducing yarn from continuous filaments is provided, comprising passinga continuously moving tow of crimped continuous filaments through a towopening and deregistering zone, deregistering said tow, slitting theresulting deregistered tow longitudinally into a plurality of fibrousstrips and collecting said strips as yarn. Preferably, the slitting iseffected after at least one spreading stage.

More specifically, in a preferred embodiment a lightweight web isproduced by passing an opened tow of crimped continuous filamentsthrough an air spreader in which the moving tow, in flattened condition,is confined between parallel walls while streams of air or othersuitable gas are directed at the tow across its full width. It has beendiscovered that it is possible in this manner to spread the tow readily,and very evenly, to great widths to produce webs of extreme fineness,such as webs containing less than about 600, e.g. 500 filaments per inchof width, and in which the average air space per fil is appreciablygreater than the diameter of the filaments, thus providing ready meansfor slitting the web longitudinally into yarn of as few as about 100filaments up to about 10,000 filaments or more as may be desired.

The average air space per fil is the average space between the filamentsof the web measured on a line in the plane of the web, perpendicular tothe longitudinal 'ice direction of the filaments of the web, said spacebeing calculated on the assumption that all the filaments are arrangedin a single plane, with no filaments crossing other filaments. It may becalculated simply from a knowledge of the average diameter of thefilaments (D the width (w) of the substantially uniform web and thenumber of filaments (n) in said width, according to the formula: AverageAir Space Per Fil=(wnD )+n.

In the preferred forms of the invention, the average air space per filis a plurality of times (e.g. five, ten or more times) as great as theaverage filament diameter. Such webs may have densities well below oneounce per square yard, e.g. to A or /2 ounce per square yard.

The invention will be described more fully by reference to the drawingsin which:

FIG. 1 is a schematic view of a process in accordance with the presentinvention illustrating tow-opening, tow spreading and the subsequentsplitting of a lightweight web to form a plurality of yarns;

FIG. 2 is an enlarged partial plan view of the slitting apparatus ofFIG. 1;

FIG. 3 is a sectional view of an air spreader particularly useful in thepresent invention;

FIG. 4 is a plan view along line -44 of the arrangement of the airopenings of the air spreader; and

FIG. 5 is another plan view along line -4-4 of an alternate arrangementof the air openings of the air spreader.

Referring to FIG. 1, a band of crimped continuous filament tow 10 isdrawn from bale 12 through a banding jet 13 com-prising a stationarycylinder 14, having a slit running lengthwise of the cylinder at itshighest point, and a curved bafile member 16 parallel to, and spacedabout the thickness of the tow 10, from the adjacent surface of saidcylinder, so that the tow band 10 passes between said baffle member 16and cylinder 14. Air under pressure is supplied to the interior of thecylinder 14 and emerges as a stream from the slit of said cylinder, theslit being cut at an angle such that the air stream has a component in adirection opposing the forward motion of the stream. The air jetpreconditions the tow for further processing by removing snags, falsetwists, straightens and flattens the tow and, if desired, spreads thetow somewhat to provide a uniform thickness. Tow band 10 is hence passedaround stationary tensioning bars 17 and 18 to help smooth and uniformlypretension said band, said bars being adjustably mounted, so that theirangle to the horizontal may be varied, to adjust the position of theband on subsequent processing equipment with which the band comes intocontact downstream of said bars.

After leaving bars 17 and 18 the band passes into the tow opening zone.The tow may be conveniently opened or deregistered, to prepare it forthe air spreading steps by subjecting it while moving in a predeterminedpath, to a differential gripping action between a plurality of pointsspaced from one another both longitudinally and traversely in the pathso that certain laterally spaced sections of the tow are positivelygripped relative to other lateral spaced sections of the tow,alternating with the grip sections, which are not gripped at all or aregripped at different relative points. In this manner there is produced arelative shifting of the adjacent filaments longitudinally along the towwhereby the crimps are moved out of registry with one another. Theshifting action is a function of the differential positive gripping ofthe tow. Preferably, although not necessarily, the differential grippingaction is such that a relative lateral displacement between adjacentfilaments of the tow is also effected, so that the combination of twotransverse filament movements brings about the complete opening of thetow.

Several methods for effecting the differential gripping action are knownin the art as well as several different apparatuses for effecting thedifferential gripping, which apparatuses deregister the tow with varyingdegrees of success. A preferred apparatus is disclosed in theaforementioned Dunlap et a1. patent.

Typically, the differential gripping action is achieved by using atleast one pair of rollers, one of which is smooth surfaced and the otherof which is patterned over its entire periphery. The most preferredapparatus comprises a plurality of such pair of rollers arranged intandem wherein one of each pair of rollers comprises a smooth surfacedroller coated with a resilient material such as rubber and the otherroller has alternating lands and grooves. Preferably, the lands andgrooves form helical threads of about 8 to 20 per inch.

Thus, the tow is passed through the nip of a pair of rolls 19 and 21prior to being passed through a second pair of rolls 22 and 23. In themost preferred embodiment, rolls 19 and 23 are the patterned rolls, suchas threaded steel rolls and rolls 21 and 22 are resilient surfacedrolls.

Each pair of rolls is individually driven at a predetermined controlledspeed. Generally, only one roll of each pair is positively driven whilethe other is in yieldable compressive contact with the driven roll androtates due to the passing of the tow between the rollers. Thedifferential gripping action and deregistering is produced by drivingthe second pair of rollers at a faster rate of speed than the firstpair. Thus, the second pair of rollers is typically driven at a rate ofabout 1.1 to about 8 times and more preferably at a rate of about 1.2 toabout 3.0 times that of the first pair.

On leaving the deregistration zone, the crimp in the tow is out ofregistry with adjacent filaments. While the tow at this point can beslit into a plurality of sections to produce yarn, it is highlypreferred to pass the tow through at least one spreading stage and morepreferably two or more spreading stages to thereby spread the tow into athin web prior to slitting into yarn. By spreading the tow to severaltimes its original width, much greater uniformity and control offilament content are obtained.

Various spreading means can be used to spread the deregistered tow intoa uniform web. Such means include mechanical spreading bars, divergingbelts, air jets and the like. The most preferred means is the air jet,also known as a banding jet.

The tow is spread as shown in FIG. 1 by means of a first spreader 24.The tow is pulled through spreader 24 by the action of driven rollers 36and 37 about which tow is S wrapped. In passing through spreader 24, thetow is spread about 2 to 4 times the width of the tow exiting from thederegistration zone. As is preferred in the present invention, the towis preferably again spread, such as in second spreader 38 wherein thespread band is again spread 2 to about 4 times the width of the webdrawn through rollers 36 and 37. Again, the web is drawn throughspreader 38 by means of another set of driven rollers 39 and 41. Thus,the spreading action preferably spreads the tow into a web at leasttwice the original width of the tow and more preferably 2 to about 10times the original tow width. In the most preferred embodiment, for theproduction of yarn of high filament uniformity, the tow is spread 4 toabout 8 times the width of the tow exiting from the deregistration zone.

From rollers 39 and 41 the spread web is passed to a slitting zonewherein the web is slit into a plurality of web sections. Numerous meansof slitting can be utilized such as roller 62 having circumferentialparallel circular V shaped grooves 63 separated by circular sharpparallel ridges 64 operating in conjunction with a hot wire apparatus 66comprising a series of spaced electrically heated wires 67 havingoperative portions penetrating said web in alignment with each ridge 64.As the web is drawn through the slitting zone by the action of anotherpair of driven rollers 68 and 69, the web is slit into narrow portionsby the groove 63 and ridge 64 portions of roller 62. Heated wires 67complete the slitting by severing cross lying filaments tying the slitwebs together. Preferably, tension is exerted on the web being slit bydriving rollers 68 and 69 at a peripheral speed in excess of the feedrate, such as about 5 percent greater than the peripheral speed ofrollers 39 and 41.

It will be readily recognized that numerous other means for slitting aweb can be used to accomplish substantially the same slitting actionwith correspondingly good results. For instance, the slitting action canbe accomplished by a knifing action which accomplishes longitudinalcutting in a manner similar to the coaction of the heated wire and ridgeand groove apparatus illustrated.

The narrow web bands produced by the cutting action are diverged to eyeguides 71 in spaced relationship to each other, from which they aretaken up with a twist on bobbin 72 mounted in ring spinner 73 of theconventional type or other yarn take up means. In such ring spinners, asis well known, the bundle of filaments passes through driven feed rolls74 and 76, stationary balloon guide 77 and moving traveler 78 mounted onreciprocating ring rails 79 before passing onto bobbin 72.

The resulting yarn is very bulky. Its strength is substantially that ofcontinuous filament yarn but it has the appearance of a staple fiberyarn because of the presence of projecting ends, on the order of about10 projecting filament ends per inch and loose loops or arches, eachmade up of a small number of crimped filaments, that is about 1 or 2filaments, lying along the main body of the yarn. Of course, the numberof projecting filament ends will vary between about 3 to 30 or more perinch, depending on the filament count, the degree of spreading, thedercgistering means used, the type of filament and the like. Knittedfabrics of this yarn have an extremely soft pleasant feel, very suitablefor baby sweaters, bulky sweaters and the like.

Alternatively, if desired, the yarn produced can be further drawn intoyarns of a lower filament count by drafting the yarn to the breakingpoint of individual filaments, thereby forming a modified staple yarn oflong variable filament length. Various apparatuses are known which willaccomplish this type of drafting and these apparatuses can be used inconjunction with the present invention to thus pass the web band througha drafting zone prior to twisting and winding on bobbins.

Referring more specifically to the air spreaders used in the presentinvention as illustrated in FIGS. 3, 4 and 5, tow 10 is passed throughspace 26 which separates air chamber 28 of plenum box 30 from back plate27. Air pressure is exhausted through slit 31 thereby impinging upon thefibrous web as it is passed through space 26. Thus, the spreadingoperation is effected on the tow as it is passed through the airspreader in a flattened condition between parallel walls while a streamof suitable gas is directed onto the tow at a right angle across itsfull width. Advantageously, the air spreading is effected in a pluralityof stages as described above, each of which spread the tow to a greaterwidth than in the preceding stage. For best results, the tow in any onestage is isolated from the effect of the following stage by passing thetow through drawing rollers such as 36 and 37, and 39 and 41 betweeneach spreading stage.

The air spreaders themselves advantageously have air delivery slits orother suitable openings in one or both of the parallel walls betweenwhich the tow passes. The slits lead from a plenum box or air chambersupplied with air at a constant pressure. In one highly effectiveapparatus, a series of slits is provided, each running in a directiontraverse to the direction of movement of the tow and so arranged thatall portions of the tow are subjected to the air stream from said slits.Surprisingly, it has been found that even when the width of the airspreader is 8 feet or more, the tow spreads uniformly from the outeredges of the tow, where the resistance to air would be expected to beless, to attain substantially the same density as the central portionsof the tow.

The pressure in the plenum chamber may vary considerably. One suitablerange is about 1 to 5 pounds per square inch gauge pressure. Higherpressures such as about 100 pounds per square inch gauge can be used,but these are generally not necessary and are economically wasteful.Surprisingly, little air is needed to expand the tow. Despite thefineness of the webs, the walls of the towconfining zones of the airspreaders need not be correspondingly close together. Thus, very goodresults have been obtained with tow confining slots one tenth inch inwidth.

Advantageously, the webs are spread to such an extent that when furtherair spreading is attempted, while the length of the web is keptconstant, the web strongly resists such spreading and returns to itsprevious width. That is, if a graph is plotted relating the air pressurein the spreader to the degree of lateral spreading of the moving web, itis found that there is substantially no additional pressure needed toeffect spreading up to a certain width, after which the air pressurerequired rises sharply. The web density at which the sharp change occursis termed herein the potential web density. This potential web densitywill vary, depending on the type of tow which is employed andparticularly on the degree of intermingling and crossing over of the towfilaments. In general, optimum tows have potential web densities belowabout one ounce per square yard and preferably less than about /2 ounceper square yard. Surprisingly, webs of such densities are easily handledand maintain their unity without disintegration during ordinaryhandling.

By spreading the web to such low densities, the filament count in theyarn can be varied to within precise limits by varying the distancesbetween the plurality of slitting means. Thus, the slitting can beeffected to produce a slit web of about 0.1 to about 6 inches or more inwidth and more preferably in the range of about 0.2 to about 1.5 inches.It will thus be readily recognized that the resulting yarn can be variedfrom a filament count of about 5 filaments or less up to about 10,000filaments or more by adjusting the width of the slit web and the densityof the web being split. Preferably, yarns having a filament count ofless than 10,000 are preferred and more preferably, yarns having a totaldenier of about 500 to 7,000.

As an example, a tow having a denier of 42,000 made up of 3 denier perfilament fibers is commonly'spread from a crimped tow in registry ofabout 4 or 5 inches to a deregistered spread tow of about 50 inches. Byslitting the spread webs to one inch webs a yarn having a filament countof 280 fils is produced. This count can, of course, be readily reducedby drafting as hereinbefore described.

In the slitting of the web, there will be portions of filaments whichcross other filaments and which are ranged at small angles, both leftand right, to the general direction of the filaments of the spread web.The hot wires or other cutting means will cut through these filaments sothat the resulting yarn will have some filaments ends giving some of theeffect of a staple fiber yarn. Because of the deregistration of thecrimped filaments in the web, the yarns produced in this manner are verybulky. When the webs are made of filaments of high tenacity such as atenacity above about 2 grams per denier, as is the case with filamentsof terephthalate polyesters, it is advantageous to use devices otherthan hot wires for cutting. Thus, a series of anvil rollers comprisingrotating, shearing discs mounted alternately on parallel axes at thesides of the discs in close contact having a scissors-like effect on thefilaments which pass between the rollers may be employed. One advantageof an anvil roller arrangement is that in addition to being used forslitting webs of stronger fibers, it gives a product free fromoccasional fused zones which may be formed when hot wires are used onthermoplastic filaments such as cellulose acetate.

The present invention is useful with all continuous filament materialswhich have been crimped prior to deregistration. The process isparticularly useful with filaments of polyethylene terephthalatepolyester and cellulose acetate of the usual acetyl content of about 54to 55 percent calculated as acetic acid. However, the invention is alsoequally applicable to other tows such as those made of other polyesterssuch as polyesters of 70/30 isophthalic and terephthalic acids and otherglycols such as dimethylolcyclohexane; linear super polyamides such asnylon 6 and nylon 66; polyacrylonitritle and copolymers ofacrylonitrile; olefinic polymers and copolymers such as isotacticpolypropylene; other organic derivatives of celulose such as esters and/or ethers of cellulose, for example cellulose propionate and celluloseacetate propionate and the like; highly esterified cellulose containingless than 0.29 free hydroxyl groups per anhydroglucose units such ascellulose triacetate; rayon and the like.

The number of filaments in the starting tow can vary within wide limitsand may range up to as high as about one million with a denier perfilament as high as about 25, that is, in the range of about 0.5 toabout 25 and more preferably in the range of 1 to 20' denier perfilament. The number of crimps per inch of tow may range up to as highas about 80, but for most end products a crimp of about 3 to 50 crimpsper inch, preferably about 3 to 30 crimps per inch of starting tow arefound to be exceptionally satisfactory.

The invention will be described more fully by reference to the exampleswhich show certain preferred embodiments of the present invention.

EXAMPLE 1 In accordance with FIG. 1, a plurality of yarns were producedfrom a single lightweight web using a band of crimped cellulose acetatetow 10* having 14,400 three denier filaments and crimped at a frequencyof 8 crimps per inch. The tow was deregistered and air spread in twostages to a web 50 inches wide, having a density of 5.2 grams per squareyard. The spread Web was fed at a rate of about 45 feet per minute to aslitting zone comprising a roll 62 having circumferential parallelcircular V-shaped grooves 63 (FIG. 2) separated by circular sharpparallel ridges 64, and a hot wire arrangement 66 having a series ofspaced electrically heated wires 67 having operative portionspenetrating said web, there along one such wire 67 for each groove 63engaged by the web, said wi res being aligned with said ridges. The webwas drawn through the slitting zone 62 by the action of a pair of rolls68 and 69 about which the slit narrow portions of the web made S-wraps.The rolls were driven at a peripheral speed 5 percent greater than theperipheral speed of rolls 39 and 41. Ridges 64 (and wires 67) werespaced one inch apart so that the web was slit into portions each of 864denier and the number of filaments was about 288. From roll 69 theseportions diverged to eye guides 71, spaced further apart, from whichthey were taken up with a twist of 1 /2 turns per inch on rotatingdriven bobbins 72 mounted in ring spinners 73 of conventional type. Insuch ring spinners, as is well known, the bundle of filaments passedthrough driven feed rolls 74 and 76, stationary balloon guides 77', andmoving travelers 78, mounted on reciprocating ring rails 79, beforepassing onto the bobbin 72.

The resulting yarn was very bulky. Its strength was substantially thatof a continuous filament yarn, but it had the appearance of a staplefiber yarn because of the presence of projecting ends (on the order ofabout 10 projecting filaments ends per inch) and loose loops or archeseach made up of a small number of crimped filaments (e.g. of one or twofilaments) lying along the main body of the yarn. Knitted fabrics ofthis yarn have an extremely soft, pleasant feel, very suitable for babysweaters, for example.

EXAMPLE 2 In the same manner as in Example 1, 3 denier per filamentpolyester terephthalate continuous filament tow having a total denier of126,000 is deregistered and spread to a Width of about 50 inches andsubsequently slit into /2. inch webs and twisted into yarn to produce abulky yarn of 1260 total denier based on the straighter length. The yarnproduced is bulky and has the characteristics of a staple yarn with thestrength of a continuous filament yarn.

The yarn is subsequently drafted to effect individual filament breakagethereby reducing the total denier to about 100 or less.

In the same manner, other continuous filament crimped fibers arederegistered, spread and slit into yarns with correspondingly goodresults.

While there have been described various embodiments of the presentinvention, the method described is not intended to be understood aslimiting the scope of the invention as it is realized that changestherein are possible. It is intended that each element cited in thefollowing claims is to be understood as referring to all equivalentelements for accomplishing substantially the same results insubstantially the same or equivalent manner. It is intended to cover theinvention broadly in whatever form its principles may be utilized.

What is claimed is:

1. A method for producing yarn from continuous filaments comprisingpassing a continuously moving tow of crimped continuous filamentsthrough a tow opening and deregistering zone, deregistering said tow,slitting the resulting deregistered tow longitudinally into a pluralityof fibrous strips and collecting said strips as yarns.

2. The method of claim 1 wherein the tow is spread into a web prior tosaid slitting.

3. The method of claim 2 wherein the tow is spread in a plurality ofstages.

4. The method of claim 2 wherein the tow is spread into a web of lessthan 1 ounce per square yard.

5. The method of claim 3 wherein the tow is slit into strips of about0.1 to about 6 inches in width.

6. The method of claim 1 wherein the slit strips are drafted prior tobeing twisted into yarn.

7. The method of claim 1 wherein the tow is slit into strips having atotal denier of about 500 to 7,000.

8. The method of claim 1 wherein the continuous filament tow ispolyester terephthalate fibers.

9. The method of claim 1 wherein the continuous filament tow iscellulose acetate fibers.

10. The method of claim 1 wherein the continuous filament tow is spreadin a plurality of spreading stages to form a Web of less than about 1ounce per square yard, subsequently slitting the web into a plurality ofstrips of about 0.1 to about 6 inches in width and having a total denierof less than 10,000 and subsequently twisting said strips into yarn.

11. An apparatus for the production of yarn from continuous filament towcomprising means for deregistering continuous filament tow, means forspreading the deregistered tow, means for slitting the spread tow into aplurality of strips and means for collecting said strips as yarns.

12. The apparatus of claim 11 wherein the means for deregistering saidtow is a patterned roll differential gripping apparatus.

13. The apparatus of claim 11 wherein the means for spreading said towis an air spreader.

14. The apparatus of claim 11 wherein the means for slitting the spreadtow into a plurality of strips is a tow separating means and a towsevering means.

15. The apparatus of claim 14 wherein the tow separating means is agrooved and ridged roller and the tow severing means is a heated wire.

References Cited UNITED STATES PATENTS 2,737,688 3/1956 Jackson 19-662,778,065 1/1957 Doleman 19-65 2,790,208 4/ 1957 Smith 19-66 2,820,2541/ 1958 Ingenthron 1951 XR 2,908,045 10/ 1959 Stevens 19-66 2,921,3591/1960 Cotumaccio.

2,996,873 8/1961 McDowell-Armstrong 57-156 3,016,581 1/1962 Smith 19-653,032,829 5/1962 Mahoney et a1, 19-65 FOREIGN PATENTS 724,777 2/ 1955Great Britain.

FRANK H. COHEN, Primary Examiner.

W. H. SCHROEDER, Assistant Examiner.

U.S. Cl. X.R.

